Mr. T. Whitelegge on Australian Pol^zoa. 21 



immersed, erect, side by side, tlieir bases separated by a thin 

 cancellated layer, forming alternate rows, and directed towards 

 the projecting nodule ; oral aperture rounded above, Avitli a 

 rather wide sinus below ; peristome slightly higher above the 

 mouth than below ; oritice nearly round, with a median pore 

 above, a depressed avicularium on each side, usually below 

 the mouth, occasionally another in front ; mandibles subcir- 

 cular, pointing upwards and outwards, a number of irregular 

 avicularian cells on the nodular projection similar to those on 

 B. anguJopora . 



Loc. Port Jackson. 



If this species should prove to be different (as I tliink it 

 will) from the fossil form described by d'Orbigny as Flahdlo- 

 pora elegans, it can remain as B. elegans. Waters. D'Or- 

 bigny's iigure (Paleont. Francj. Bryoz. tom. v. pi. 661) cer- 

 tainly resembles the recent form. The same may be said of 

 B. unibonata, which comes nearest to d'Orbigny's species ; if 

 it were not for the elevated nodules, the last-named might 

 pass for the fossil species. I have examined about nine 

 specimens in all, two of them being less than I of an inch in 

 their greatest diameter, which, when placed on their convex 

 edges and viewed from above, greatly resemble B. angulo- 

 poi-a, and if a little less compressed might be mistaken for that 

 species at first sight. The avicularian cells are present in 

 both specimens on the nodular projection and the semilunar 

 slits on various parts of the zoarium. The slits can be seen 

 even in very old specimens scattered about on the surface. 

 It is not difficult to trace the stages by which the conical 

 form might be changed into the ilabellate, and afterwards 

 into the lobate form, which has probably taken place. If 

 we imagine the internal cancellated layer to become less 

 developed, accompanied by a gradual compression and the 

 addition of a few more rows of zooecia towards the outer mar- 

 gin, we can easily see that we should have a form like B. 

 elegans^ which is in reality only a flattened cone with the 

 base widely extended, and in B. umhonata the flabellate form 

 is changed into a lobate one by the non-development of a 

 portion of the colony. So that the broad non-divided end of 

 the last-named species and the nodular portion of the former 

 correspond with the apex of the cone. 



POSTSCUIPT. — Since the foregoing was written I have been 

 fortunate in obtaining some living examples of Bipora pJiUip- 

 yineasis (Busk), which I have had under observation for three 



